LTREB: Collaborative Research - Long-Term Dynamics of Amphibian Populations Following Disease-Driven Declines

Award Period
Award Amount
Agency Name
National Science Foundation
Award Number
PI First Name
PI Last Name
Roland Knapp
MSI People
Area/s of Research
Ecology and Evolution


The proposed research builds on data from a long-term study of the population dynamics of mountain yellow-legged frogs (Rana sierrae and Rana muscosa) in the California Sierra Nevada mountains, and the impacts of the amphibian chytrid fungus, Batrachochytrium dendrobatidis (= Bd), as it has invaded and spread through frog populations in hundreds of high elevation lakes. In most cases, invasion of Bd results in epizootics of the disease chytridiomycosis, rapid frog population declines, and local extinctions, but in some cases long-term persistence of frog populations occurs with Bd in an enzootic state.

The proposed research will investigate the patterns of change in both the frog and the fungus as Bd swept across the Sierra Nevada, and the implications of these changes for Bd virulence and frog resistance/tolerance to infection. This will be accomplished through a combination of cutting-edge genomic analysis of skin swab samples, surveys of field populations, collection of Bd cultures and frog mucosal samples from field populations, and laboratory experimentation on Bd virulence and frog susceptibility.

Intellectual Merit:

Outbreaks of emerging infectious diseases are increasingly recognized as major threats to wildlife populations, with important implications for species conservation. The initial invasion of a novel pathogen into susceptible host populations often results in epizootics characterized by high host mortality and population declines, during which time strong selection can occur on both the host and pathogen. Chytridiomycosis has had catastrophic effects on amphibians worldwide, with numerous species extinctions documented in recent decades and many more at risk of Bd-caused declines.

The proposed research will contribute to the understanding of the role of infectious diseases, such as chytridiomycosis, as agents of evolutionary change in natural populations. The research will make use of recent advances in molecular approaches, and the extensive dataset and archive of samples from the R. sierrae/R. muscosa-Bd system, to investigate how both host and pathogen populations change during the transition from pre-pathogen arrival, to disease epizootic, to enzootic disease, to potential recovery of the pre-disease host population abundances. This dataset will be used to investigate the genetic basis for differences in host resistance/tolerance and pathogen virulence.

Broader Impacts:

This proposed research has general implications for the conservation and long-term survival of wildlife species threatened by emerging infectious diseases, with specific relevance for R. sierrae/R. muscosa. Because of the severity of the declines experienced by these species, they are currently the focus of intense multi-agency conservation efforts. As such, the proposed study presents an unusual opportunity to conduct research that could provide crucial guidance to efforts aimed at reversing the decline of these species, including re-establishing R. sierrae/R. muscosa in Bd positive areas from which they were previously extirpated by Bd epizootics.

The results will be disseminated broadly through presentations at national and international conferences, social media, open access publications, and publically available data archives. The research program will contribute to undergraduate education at UCSB and UC Berkeley, through integration with undergraduate general education courses in disease ecology and global change biology (reaching ~350 students per year). Undergraduate and graduate students from diverse backgrounds will be recruited to participate in both field and laboratory studies related to the proposed project. The considerable public visibility of, and interest in, amphibian declines will provide opportunities to develop public outreach activities, including presentations to conservation organizations and K-12 schools.